CVE-2025-68780
Description
In the Linux kernel, the following vulnerability has been resolved: sched/deadline: only set free_cpus for online runqueues Commit 16b269436b72 ("sched/deadline: Modify cpudl::free_cpus to reflect rd->online") introduced the cpudl_set/clear_freecpu functions to allow the cpu_dl::free_cpus mask to be manipulated by the deadline scheduler class rq_on/offline callbacks so the mask would also reflect this state. Commit 9659e1eeee28 ("sched/deadline: Remove cpu_active_mask from cpudl_find()") removed the check of the cpu_active_mask to save some processing on the premise that the cpudl::free_cpus mask already reflected the runqueue online state. Unfortunately, there are cases where it is possible for the cpudl_clear function to set the free_cpus bit for a CPU when the deadline runqueue is offline. When this occurs while a CPU is connected to the default root domain the flag may retain the bad state after the CPU has been unplugged. Later, a different CPU that is transitioning through the default root domain may push a deadline task to the powered down CPU when cpudl_find sees its free_cpus bit is set. If this happens the task will not have the opportunity to run. One example is outlined here: https://lore.kernel.org/lkml/20250110233010.2339521-1-opendmb@gmail.com Another occurs when the last deadline task is migrated from a CPU that has an offlined runqueue. The dequeue_task member of the deadline scheduler class will eventually call cpudl_clear and set the free_cpus bit for the CPU. This commit modifies the cpudl_clear function to be aware of the online state of the deadline runqueue so that the free_cpus mask can be updated appropriately. It is no longer necessary to manage the mask outside of the cpudl_set/clear functions so the cpudl_set/clear_freecpu functions are removed. In addition, since the free_cpus mask is now only updated under the cpudl lock the code was changed to use the non-atomic __cpumask functions.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
OS impact
SUSE Affected 1 release
| Version | Status | Fixed in |
|---|---|---|
| — | Affected | — |
Debian Fixed 5 releases
| Version | Status | Fixed in |
|---|---|---|
| trixie | Fixed | 6.12.69-1 |
| sid | Fixed | 6.18.3-1 |
| forky | Fixed | 6.18.3-1 |
| bullseye | Fixed | 6.1.162-1~deb11u1 |
| bookworm | Fixed | 6.1.162-1 |
References
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.